Device and method for the detachment of a tube blank from a support core

ABSTRACT

The invention relates to a method and a device for the removal of a tube blank ( 3 ) located on a support core ( 2 ). The tube blank ( 3 ) is detached from the support core ( 2 ) by means of the introduction of a medium through a device ( 10 ), whereby a detachment may be alternatively or additionally achieved by the application of a vacuum to a sleeve ( 4 ) enclosing the tube blank ( 3 ).

FIELD OF THE INVENTION

The invention relates to a method and an apparatus for the detachment ofa tube blank from a support mandrel. The method and the apparatus aresuitable in particular for the detachment of a tubular air-spring blankfrom a support mandrel.

BACKGROUND OF THE INVENTION

DE 27 50 6 42 C2 discloses a method and an apparatus for producing anydesired blanks from elastomeric material. As disclosed, in order toremove a core, the product is put onto a carpet having a highcoefficient of friction, and a longitudinal movement is superimposed onthe carpet. The carpet is preferably made of rubber grooved in thetransverse direction. This reference further describes how the core,before the product is applied, can be covered with a suitable separatingagent, such as a silicone solution for example, and how compressed airis introduced into the product in order to achieve a certain enlargementof the product.

DE 21 40 9 56 C3 describes an apparatus for producing elbow hoses onmandrels. In this apparatus, an elbow blank is pushed onto the mandrelby means of a push cylinder. The push cylinder, which can be attached tothe rear end face of the elbow blank in a pressure-tight manner, ensuresthat, when the elbow blank is pushed onto the mandrel, the air containedin the blank volume does not escape past the push cylinder but leads toan air cushion between the elbow blank and the mandrel. This air cushionfacilitates the push-on operation.

SUMMARY OF THE INVENTION

The invention provides an apparatus and a method with which tubularblanks of finite length can be easily separated from the supportmandrel, so that further processing of the blank can be quicklyaccomplished, and reuse of the support mandrel is ensured.

According to embodiments of the invention, by the insertion of a devicefor introducing a medium at one end of the support mandrel between theextruded blank and the support mandrel and by the injection orintroduction of a medium by means of the device, an air cushion or filmis achieved. As a result, the blank, which typically sticks to thesupport mandrel, is detached and a separating gap is produced. On thisaccount, easy removal of the support mandrel is possible.

In order to ensure even and complete detachment of the blank, the end ofthe blank which is opposite the device is sealed off, or a second deviceis inserted between the blank and support mandrel, so that the blankdoes not stick at a point or over a certain section of the circumferenceof the support mandrel. If the blank is sealed off at one end, forexample, by fitting a clip or a closure ring, the blank is completelydetached up to the sealing point.

For easier detachment of the blank from the support mandrel, provisionmay be made for liquid or powdery separating agents that assist or makepossible easy separation to be added to the medium. The separatingagents can be applied to the support mandrel before the fabrication ofthe tube blank. The support mandrel may be provided with the non-stickcoating.

After the detachment of the blank from the support mandrel, provisionmay be made for the latter to be pushed out by the medium, for example,if the support mandrel is partly formed as a hollow body and the mediumaccumulates in this hollow body, or for the support mandrel to be pulledout of the inflated and widened blank by an extraction device. Thesupport mandrel is advantageously pulled out in an automatic orsemiautomatic manner.

In one aspect, in order to prevent uncontrolled widening or partialwidening of the blank, provision is made in an advantageous developmentfor the blank located on the support mandrel to be inserted into asleeve before the injection of the gaseous medium. This sleeve limitsthe expansion of the blank, where the inside diameter of the sleeve isat least slightly larger than the outside diameter of the blank.

In order to be able to introduce the medium at any desired location oralso centrally inside the device, the device is fastened to the sleevein such a way that the blank is clamped in place between the sleeve andthe device, preferably in a sealing manner. In this way, it is possibleto achieve complete detachment and separation of the blank from thesupport mandrel with only one feeding point for the medium.

To assist in the detachment of the blank from the support mandrel,provision is made for a vacuum to be generated in the sleeve, in whichcase, as an alternative to the method of introducing a medium, such as,for example, air, water or oil, provision is made for the blank on thesupport mandrel to be sealed off from the sleeve and for a vacuum to begenerated in the sleeve. In this way, the blank is separated from thesupport mandrel solely on account of the vacuum. To this end, it may benecessary for a mechanism which provides the inflow of the ambient airto be incorporated in the bearing surface of the support mandrel.

An apparatus according to the invention provides for a device forintroducing a medium at one end of the support mandrel to be arrangedbetween the blank and the support mandrel, and for there to be feedingelements for introducing the medium between the blank and the supportmandrel. A gap or a film is produced in a specific manner between thesupport mandrel and tube blank by the apparatus. As a result, thesupport mandrel and tube blank can easily be released from one another.

An advantageous configuration of the invention provides for a sleeve tobe arranged around the blank. This sleeve is closed at least at one ofits ends by the device, and the blank advantageously is sealed off fromthe support mandrel at the other end. This configuration may lead tolimitation of the radial expansion of the blank and, to completedetachment of the blank from the support mandrel. In addition, onaccount of controlled widening and by avoiding excessive expansion, thematerial is protected and quality improvement is achieved at the tubeblank.

To ensure that the sleeve is reliably sealed off from the environment orfrom the device, provision is made for the device to be capable of beingfastened to the sleeve, preferably via clamping cylinders, so that thedevice moves onto the support mandrel and in the process clamps the tubeblank in place between it and the sleeve in a sealing manner.

In an alternative configuration of the apparatus, provision is made fora sleeve arranged around the blank to be provided with sealing elementsfor forming an essentially airtight space together with the blank. Also,a device may be provided for generating a vacuum in the space formed bythe sleeve and the blank, so that the blank is separated from thesupport mandrel on account of the vacuum. Advantageously provided in thesupport mandrel for this purpose are air-inlet arrangements which allowthe ambient air to flow into a gap forming between the support mandreland the tube blank.

To facilitate the manipulation of the bulky and heavy support mandrel,provision is made for the sleeve to be designed to be split or hinged inits longitudinal extent; so that the support mandrel together with theblank can be inserted into the swung-open sleeve and the latter can thenbe closed. It is, of course, also possible to design the sleeve in onepiece, in which case the support mandrel must then be pushed into thissleeve.

In order to avoid sticking of the tube blank, preferably of anunvulcanized tube blank, to the inside of the sleeve, the latter isadvantageously provided with a repellent coating, for example,Polytetrafluoroethylene (PTFE) coating.

In order to achieve certain preforming by appropriate widening duringthe introduction of the medium, a conical design of the sleeve may beprovided. This leads to different radii in the course of thelongitudinal extent of the tube blank on account of different wideninguntil the tube blank bears against the inside of the sleeve. Such aconical design of the tube blank is advantageous in particular for theproduction of air springs. In deviation from a conical design, thesleeve may have various geometries, such as, for example, multipleconicity or a corrugated shape, in order to permit correspondingadaptation of the blank to various intended uses. By inflation whichvaries in this way, adapted products from the preliminary materialsshaped cylindrically beforehand can be vulcanized in a subsequentprocessing step.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other aspects and advantages will be better understoodfrom the following detailed description of embodiments of the inventionwith reference to the drawings, in which:

FIG. 1 shows a side view of the apparatus;

FIG. 2 shows a front view of the apparatus with swung-open sleeve;

FIG. 3 shows a front view of the apparatus with swung-shut sleeve andfastened feeding device; and

FIG. 4 shows a detailed view of the apparatus according to FIG. 3.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Shown in FIG. 1 is a side view of an apparatus 1 in which a supportmandrel 2 with an extruded tube blank 3 is inserted into a swung-opentwo-piece sleeve 4, which includes a bottom part 4 a and a top part 4 b.In this aspect of the invention, two apparatuses 1 are mounted back toback on the frame 20, with the sleeve 4 is mounted on a frame 20. In oneaspect of the invention, the sleeve 4 may be provided to preventuncontrolled widening or partial widening of the blank. That is, thesleeve may limit the expansion of the blank, where the inside diameterof the sleeve is at least slightly larger than the outside diameter ofthe blank. This added space allows a gap or a film to be produced inbetween the support mandrel 2 and tube blank for easy removal of theblank.

The top part 4 b of the sleeve 4, relative to the sleeve bottom part 4a, is swung from the open position shown into a closed position via alifting cylinder 6. The sleeve 4 can be locked in the closed state andhas an inside diameter which is greater than the outside diameter of thetube blank 3. The hinged sleeve facilitates the manipulation of thesupport mandrel so that the support mandrel together with the blank canbe inserted into the swung-open sleeve 4 and the latter can then beclosed. It is, of course, also possible to design the sleeve in onepiece, in which case the support mandrel 2 will be pushed into thissleeve.

In one implementation, the tube blank 3 comprises at least one rubber orplastic layer which has been applied to the support mandrel 2; however,the rubber mixture is preferably encased with strength members on thesupport mandrel 2 in order thus to obtain a thin-walled and robust tubeblank 3. These strength members are, for example, fibers, threads, wiresor wovens or nonwovens. At the end of an extruder line, in which such atube blank 3 is applied to the support mandrel 2, the support mandrel 2is received at the end faces and are put into the sleeve 4 in order tobe separated from one another before the vulcanization.

The apparatus 1 according to FIG. 1 is shown turned through 90° in FIG.2. In this view, it is shown that the support mandrel 2 with the tubeblank 3 is longer than the sleeve 4. An attachment piece 7 projects fromone side of the mandrel 2 and is designed as an extension elementarranged on the sleeve, in the exemplary embodiment in FIG. 2, in orderto permit easy adaptability to various production requirements. Thesupport mandrel 2 projects from the sleeve 4 at the end faces on bothsides, and the sleeve 4, after the insertion of the blank 3 togetherwith the support mandrel 2, is locked via a locking cylinder 5. Both thelifting cylinders 6 and the locking cylinder 5 preferably workhydraulically or pneumatically, although other working principles arepossible and are envisaged.

Arranged on the left-hand end of the blank 3 is a device 10 forintroducing a medium, which is pushed in between the support mandrel 2and the blank 3 with its frustoconical end. In one aspect of theinvention, the blank 3 can be manually released from the support mandrel2 beforehand and widened in order to make it easier to push in thefrustum of the device 10. In this case, the device 10 is designed insuch a way that the end of the device 10, opposite the frustoconicalend, is closed. Also arranged on the device 10 are clamping cylinders12, with which the device 10 can be clamped relative to the sleeve 4.

A clamped state of the device 10 relative to the sleeve 4 is shown inFIG. 3, in which the clamping cylinders 12 engage in a collar-likewidening of the sleeve 4 and pull the frustoconical portion of thedevice 10 toward the sleeve 4. In the process, overall, the supportmandrel 2 is shifted to the right, as indicated by the arrow at theright-hand end.

The arrangement illustrated in FIG. 3 is shown in the form of asectional representation in FIG. 4. In this representational view, theclamping of the device 10 relative to the sleeve 4 is provided via theclamping cylinders 12. Also, the clamping of the tube blank 3 is shownbetween the frustoconical end of the device 10 and the sleeve 4. Byhaving the device 10 fastened to the sleeve 4 in such a way that theblank 3 is clamped in place between the sleeve 4 and the device 10,introduction of the medium at any desired location or also centrallyinside the device is possible. In this way, it is possible to achievecomplete detachment and separation of the blank 3 from the supportmandrel 2 with only one feeding point for the medium.

In order to ensure even and complete detachment of the blank, the end ofthe blank which is opposite the device 10 is sealed off, or a seconddevice is inserted between the blank 3 and support mandrel 2, so thatthe blank does not stick at a point or over a certain section of thecircumference of the support mandrel 2. If the blank is sealed off atone end, for example, by fitting a clip or a closure ring (as isillustratively shown in FIG. 2 at reference “C”), the blank iscompletely detached up to the sealing point. Furthermore, a feedingelement 11 is arranged on the side of the device 10 which is remote fromthe frustoconical end. Compressed air or another suitable medium such aswater or oil can be introduced into the device 10 via the feedingelement 11.

As can be seen from the figures, the support mandrel 2 is not completelyhollow but rather has only one end-face bore for accommodatingmanipulating elements, so that, if a positive pressure is introduced viathe feeding element 11, the medium can penetrate only between the blank3 and the support mandrel 2 and thus detaches the blank 3. Bores,grooves or other passages can be provided in the frustoconical end forsimple introduction of the medium. In such a scenario, these bores,grooves or other passages are advantageously to emerge as close to theoutside diameter of the support mandrel 2 as possible.

After the positive pressure has been introduced, the blank 3 will bewidened until part of the outer surface touches the inside diameter ofthe sleeve 4. The medium is introduced until the blank 3 has beencompletely or substantially completely released from the support mandrel2 over the entire length and the medium comes out at the other end, orthe support mandrel 2 is pushed out by the slight positive pressure.After detachment of the blank 3, the support mandrel 2 can be pulled outat the opposite end of the device 10. After complete removal of themandrel, the device 10 is released from the sleeve 4, which is swungopen, and the blank 3 can be removed.

In order to avoid sticking of the blank 3 to the inside of the sleeve 4,the latter may be provided with a non-stick coating, for example, wettedor smeared with PTFE and/or with a separating agent which preventssticking. In addition, liquid or powdery substances can be introducedwith the medium in order to facilitate detachment. Likewise, provisionmay be made for the end of the blank 3, which is remote from the device10, to be sealed off in order to build up a pressure between the supportmandrel 2 and the blank 3. By a configuration of the sleeve 4, variousoutside diameters of the tube blank can be pre-expanded in order tofacilitate further processing of the tube blank 3.

In addition to, or as an alternative to, the detachment and the removalof the tube blank 3 from the mandrel via compressed air, provision ismade for this to be assisted or replaced via a vacuum process. In thisaspect, the intermediate space between sleeve 4 and tube blank 3 issealed off and a vacuum is generated. Depending on requirements,different tube blank lengths can be processed via the extension elements7.

While the invention has been described in terms of embodiments, thoseskilled in the art will recognize that the invention can be practicedwith modification within the spirit and scope of the appended claims.

1. A method for the detachment of a tube blank from a support mandrel,comprising: inserting a device at one end of the support mandrel;inserting the blank on the support mandrel into a sleeve for limitingradial expansion of the blank, attaching expansion pieces to the sleeveto accommodate the length of the blank, and introducing a medium betweenthe blank and the support mandrel.
 2. The method as claimed in claim 1,wherein an end of the blank which is opposite the device is sealed offfrom the support mandrel.
 3. The method as claimed in claim 1, furthercomprising providing a closure element on the blank in order to ensurecomplete detachment of the blank from the support mandrel.
 4. The methodas claimed in claim 1, wherein the blank is detached from the supportmandrel by expanding the blank away from the surface of the supportmandrel.
 5. The method as claimed in claim 1, further comprisingintroducing liquid or powdery separating agents with the medium.
 6. Themethod as claimed 1, further comprising, after detachment of the blankfrom the support mandrel, pushing out the blank from the support mandrelby the medium or the support mandrel is moved out.
 7. The method asclaimed in claim 1, further comprising fastening the device to thesleeve in such a way that the blank is clamped in place between thesleeve and the device.
 8. The method as claimed in claim 1, furthercomprising generating a vacuum in the sleeve.
 9. The method as claimedin claim 1, wherein the medium penetrates only between the blank and thesupport mandrel and thus detaches the blank from the support mandrel.10. The method as claimed in claim 1, further comprising providing anon-stick surface provided on an interior surface of the sleeve.
 11. Anapparatus for the detachment of a tube blank from a support mandrel,comprising: a device for introducing a medium at one end of the supportmandrel, the device being arranged between the blank and the supportmandrel; and a feeding element provided at the device and forintroducing the medium between the blank and the support mandrel, theapparatus further comprising a sleeve which is arranged around the blankand which has a variable in length via attachment pieces.
 12. Theapparatus as claimed in claim 11, wherein the sleeve is closed at leastat one end by the device, the blank being sealed off from the supportmandrel at the other end.
 13. The apparatus as claimed in claim 12,wherein the sleeve includes a first part hinged to a second part along alongitudinal extent.
 14. The apparatus as claimed in claim 13, furthercomprising a closing mechanism for closing the first part or the secondpart of the sleeve when the blank and support mandrel are insertedtherein.
 15. The apparatus as claimed in claim 12, wherein the device isfastened to the sleeve.
 16. The apparatus as claimed in claim 12,wherein an inner diameter of the sleeve is larger than an outer diameterof the blank thus providing provision for expansion of the blank. 17.The apparatus as claimed in claim 12, wherein the sleeve is cylindricalor contoured.
 18. The apparatus as claimed in claim 11, furthercomprising a closure device at an end of the blank, remote from thedevice.
 19. A method for the detachment of a tube blank from a supportmandrel, comprising the steps of inserting a device at one end of thesupport mandrel; and generating pressure by introducing a medium betweenthe blank and the support mandrel by the device until the blank isseparated from the mandrel, and introducing additional medium until thegenerated pressure moves the mandrel outward.